Genome-wide survey of Gγ subunit gene family in eight Rosaceae and expression analysis of PbrGGs in pear (Pyrus bretschneideri)

Background: Heterotrimeric G-proteins, composed of G alpha, G beta and G gamma subunits, are important signal transmitters, mediating the cellular response to multiple stimuli in animals and plants. The G gamma subunit is an essential component of the G-protein, providing appropriate functional specificity to the heterotrimer complex and has been well studied in many species. However, the evolutionary history, expression pattern and functional characteristics of G gamma subunits has not been explored in the Rosaceae, representing many important fruit crops. Results: In this study, 35 G gamma subunit genes were identified from the eight species belonging to the Rosaceae family. Based on the structural gene characteristics, conserved protein motifs and phylogenetic analysis of the G gamma subunit genes, the genes were classified into three clades. Purifying selection was shown to play an important role in the evolution of G gamma subunit genes, while a recent whole-genome duplication event was the principal force determining the expansion of the G gamma subunit gene family in the subfamily Maloideae. G gamma subunit genes exhibited diverse spatiotemporal expression patterns in Chinese white pear, including fruit, root, ovary and bud, and under abiotic stress conditions, the relative expression of G gamma subunit genes were up-regulated or down-regulated. In addition, seven of the G gamma subunit proteins in pear were located on the plasma membrane, in the cytoplasm or nucleus. Conclusion: Overall, this study of the G gamma subunit gene family in eight Rosaceae species provided useful information to better understand the evolution and expression of these genes and facilitated further exploration of their functions in these important crop plants.